UFC 3 -520-01
June 10, 2002
10-4.1.2 Electrical system grounding is not replaced by communications system
grounding. Instead, communications systems grounding supplements the existing
grounding s ystem with additional bonding between communications cable pathways
between telecommunications entrance facilities, equipment rooms, and
telecommunications closets. Significant differences in ground potentials can exist even
in a well-designed building during electrical transients. By bonding additional
conductors throughout the communications systems to the facility grounding system,
the overall system can be made more resistant to these transients. Note that these
additional conductors primarily serve to reduce or eliminate ground potential differences
in the communications system while still satisfying NEC grounding criteria.
10-4.1.3 Communications system grounding and bonding is intended to accomplish its
purpose by the following methods:
. The potential between different ground points depends
communications systems reduces the impedance to ground throughout the facility,
thereby improving the ground e qualization.
Diversion. By installing additional ground connections throughout the
communications systems, electrical transients are more likely to be diverted to ground,
thereby minimizing the effect on the communications systems.
Coupling. By having bonding conductors close to communications
cables, mutual coupling between the two is improved. During electrical transients, this
coupling can partially cancel the transient's effects. Note this is independent of any
shielding that might also be provided for the conductors.
Connection to the Grounding Electrode.
10-4.2.1 A suitable connection to ground has to be established for the communications
systems. The preferred grounding method is to connect to the facility's electrical
service grounding electrode system. The communications systems are powered from
the electrical system and all cabling, power and communications, need to be effectively
at equal potential with respect to ground. NEC Article 800.40 (2002 Edition) establishes
the grounding requirements.
10-4.2.2 Separate grounding electrodes are not normally necessary for the
communications systems. NEC Article 800.40 (2002 Edition) allows the use of separate
grounding electrodes if there is no electrical service ground or if additional grounding is
needed to improve the overall impedance to ground . Whenever a separate grounding
electrode is used, it must be bonded to the existing grounding electrode system as
required by the NEC.